Monday, March 7, 2016

Chimney Fire!

I hadn't originally intended to write a post about this, but after further reflecting on the event and on the purpose of this blog, I'm hoping that by sharing our experience, someone else will benefit from our misfortune.  On a mid-February Saturday morning, Nancy and I were fortunate to wake up unscathed in our own bed.  We had a chimney fire in the night, and God was truly looking out for us because no damage occurred.  Here is what happened:

Like I always do each winter night, I had filled the Margin Gem's firebox with the largest chunks of wood possible.  Usually, I then almost completely close all drafts and dampers so that the fire burns slowly all night long.  This assures us of a nice bed of coals to rekindle in the morning, a tank of hot water for our morning showers, and fairly steady heat being emitted in the kitchen all night.

On that particular Friday night, I loaded the stove and then thought that I'd leave the drafts and dampers open for a little while to let the wood ignite better before shutting everything down.  Unfortunately, my forgetfulness kicked in, and I went to bed without shutting anything.  Thus, the firebox was completely full, and the stove was wide open.  This was clearly operator error, and I'm duly embarrassed.

I awoke in the wee hours of the morning to go to the bathroom and thought I'd run downstairs and put some more wood in the stove.  I sometimes do this when I know that the fire has had time to burn down enough that there will be room for another piece of wood.  When I opened the stairway door into the kitchen, I could immediately tell that the kitchen was much warmer than it ordinarily should have been.  This was due to the fact that the fire had burned so rapidly--not due to the chimney fire.  When I removed the front lid over the firebox, I was shocked to see that only a few coals remained on the grate where normally there would have been a lot of coals and some as-yet-unburned pieces of wood.  That is when I investigated and noticed that the draft, the oven damper, and the chimney damper were all open.  I still didn't know that we had had a chimney fire at that point, though.

When I began to rekindle the fire by putting a few pieces of wood on the coals, I immediately noticed that the stove was not drawing correctly, and then I became aware that every time I opened a lid, a little noise came from the stovepipe.  That was when I realized that we had had a chimney fire.  By that time, the wood that I had just put in the stove had caught fire, and there was sufficient draft to carry away the smoke, so there was not much that I could do except close the oven damper and the draft and let the fire burn itself out so that I could clean and inspect the flue in the morning.

Fortunately, we had cleaned the chimney and stovepipe during the first part of February, so there was not as much creosote accumulated in the flue as there might have been.  In my opinion, this is the major factor which kept this event from being a full-fledged disaster.  The other thing that helps us is our chimney.  The Margin Gem cookstove is vented through the masonry chimney which is original to our 98-year-old-farmhouse, but the chimney has been professionally sealed and lined with a heavy-guage stainless steel lining with quite a bit of space between it and the brickwork. Thus, there is an extra heat barrier between the structure of the house and the flue.

The next morning, I hurried to take the stovepipe down and sweep and inspect the chimney.  I didn't snap any photographs because I initially didn't plan on blogging about this event and I was in a huge hurry to get the fire going again because we had a ton of laundry to do and needed it to heat our water.

You might think that a chimney fire would burn away all of the creosote that is in the flue.  In my experience, what happens is that the creosote sort of bubbles and puckers so that it actually protrudes into the flue and impedes the draft.  It becomes sort of like the carbonized stuff on the floor of your oven after a pie boils over.  Because it is so brittle, it is easy to clean out of the chimney.

In my eighteen years of cooking with wood cookstoves, this is the second chimney fire that I have experienced.  Both events have some things in common: creosote, a hot fire, and an open oven damper.

The Margin Gem's oven damper in the open position.
It is the lower lever on the left with the black sphere on the bottom.

The first one occurred in the summer of 2004 (I remember this because Nancy and I were engaged).  I had baked bread in the Qualified on a late spring or summer afternoon, and after the bread came out of the oven, I opened the oven damper to let the heat escape up the chimney rather than heat up the house.  I knew that the chimney needed cleaning, but did not dream that a chimney fire would result.

All of this serves to remind me of a short quote from Gladys Dimock that Jane Cooper included in her 1977 book Woodstove Cookery: At Home on the Range: "Except for starting the fire, I always keep the oven damper closed.  This prevents the flames from going up the chimney and igniting any creosote.  We had a chimney fire once because the damper was left open.  Never again."

During summer use, I still open the oven damper when I'm finished cooking to let the heat escape up the chimney, but I'm careful about it.  Obviously, keeping creosote at a minimum is quite important too.

If you discover that you have an active chimney fire, the first thing to do is close all dampers and drafts on your stove because you want to deprive the fire of its source of oxygen.  This was sufficient to extinguish the 2004 chimney fire.

We keep a chimney fire extinguisher handy at all times.  This is a stick-shaped thing somewhat similar to a flare that is activated and put into the firebox.  I've never used it, though.

Another method for extinguishing a chimney fire which I've only read about is to put water-soaked newspapers on top of the fire in the firebox.  The idea is that the heat of the fire will cause the water in the papers to turn into steam, which will then travel up the chimney and extinguish the burning creosote.

If any of you have further information about chimney fires, please share it in the comments below.  We all should want to be responsible woodburners because operating our stoves safely results in fewer hazards and insurance claims, which in turn keeps us safe and our insurance rates low.

11 comments:

  1. We had a chimney fire a couple of years ago after my husband got a little over enthusiastic with feeding the fire and also left the damper open. I'm glad to say that all was well after the incident and I am ever vigilant these days.

    Our Rayburn heats the house, the water, and cooks like a dream (except when he sulks). I wax lyrical about how special it feels to be cooking on a stove like that; it feels peaceful and right, in a way which doesn't happen if I use the gas/electric stove.

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  2. Glad you're all ok!

    We had a (thankfully minor) chimney fire our first winter in the house. There were a couple things likely at fault.

    We hadn't cleaned the chimney as the former owners told us they had done it after their last fire in the spring. The guy who did the chimney repair said that either they'd lied, or that it hadn't been very well done at all, as there was a couple years worth of creosote build up.

    The repair guy also told us that the pipe he pulled down showed some very deep scratches that were not new. He thought that whoever had been cleaning the metal pipe had been using a masonry brush, scratching the pipe and allowing creosote to build up extra deep in spots.

    It was towards the end of a really long winter, and we, like alot of folks in the area that winter, had run through our good wood and were picking through the oldest of the "newer" wood, it's entirely possible that the pieces were picked were just not dry enough and produced extra creosote.

    Luckily the fire happened while I was awake. I was infact sitting near the stove reading when I realized that I could hear the fire burning.....OVER MY HEAD. A run outside showed sparks, and what looked like flames, coming out of the top of the chimney. I grabbed the little fire extinguisher we keep nearby and put out fire in the stove, and then closed all dampers. A check of the chimney still showed sparks and apparent flames, so 911 was called. In the few minutes it took for the firemen to come the apparent flames had disappeared and most of the sparks stopped. The firemen later told me that putting out the fire and closing the damper like I'd done had indeed stopped the fire, albeit more slowly than I'd realized. They also told me that likely what I'd taken as flames had probly been the fire in the pipe reflecting off of the smoke coming out the top of the chimney as the fire hadn't been THAT big. Thankfully I'd caught it before it spread beyond the chimney pipe.

    We are now extra OCD about making sure that the chimney is cleaned on schedule, and that we have more wood on hand than we think we're going to need for the winter. Its not an experience we wish to repeat!

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  3. Keep a large box of baking soda handy. If the fire is overheating, throw some into the firebox. It releases co2 and will damp down the fire. I've used this a lot since I learned about it and it does work.

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  4. I really appreciate your work especially the research part of it which made the whole point very easy to understand, thanks for posting this blog
    chimney sweep Auckland

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  5. I'm very thankful that you did a post on this. We're under contract to buy a house that has a wood stove and I came across your blog while doing research. I know NOTHING about wood stoves, other than they get hot, so this was extremely helpful to read. Your whole blog is great, thank you for sharing for knowledge.

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    1. Thanks, Jamie, for your kind words!

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  6. I am curious about how much creosote folks are finding when they have their chimney cleaned. We have had our margin gen for four years and when it was installed along with a new straight flue, I was concerned about not having an elbow in the stovepipe that could be used as a cleaning port which we couldn't accommodate with our clearances.

    We burned dry wood in it the first year but damp-ish wood the second so were were a little worried about potential creosote build up. After year two we had it cleaned professionally for the first time. However, the cleaner told us that he got less than a cup of creosote out of the chimney so we haven't been worrying about creosote much ever since. I am curious about what others are finding in theirs and if you folks getting chimney fires have elbows in your stovepipes. Anyone burning softwood?

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    1. Welcome, Greg! Thanks for your comment. I hope others will reply, but here is what I have learned/experienced:

      As you can see from the pictures of our stove on the blog, we have two elbows in the stovepipe, and then there is another 90-degree angle just inside the chimney. The Qualified Range was vented in this same configuration.

      With the Qualified, we had creosote, but usually there wasn't that much. The chimney still had to be cleaned, but once or twice a year was sufficient.

      With the Margin Gem, we clean the chimney at two-month intervals or even more frequently, and we get quite a bit of creosote.

      We burn only hardwood.

      I recently watched an online video about creosote buildup in chimneys, though, which corroborated everything I've said on the blog about our additional creosote buildup with the Margin Gem. The gist of the video was that creosote buildup is entirely dependent on flue temperatures rather than what kind of wood you burn or anything else.

      This makes a lot of sense to me because, since the Margin Gem is airtight and can be dampered down so tightly, we load her up in the morning before work and damper her down so that she will hold the fire all day and heat the house in our absence. We do the same before going to bed at night. That means that in a twenty-four hour time period, at least sixteen hours are spent in a slow burn, which naturally results in lower flue temps--and hence the increased creosote buildup.

      We loaded up the Qualified in the same way, at the same times of the day, but because it was not airtight, the fire would burn hot and quickly and be completely out by morning or by the time we got home in the late afternoons.

      What are your firing habits? Also, is your Margin Gem outfitted with a water jacket or water reservoir? Those would both absorb some BTUs that would ordinarily escape up the chimney, too. Let me know. It's a great discussion to have.

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  7. Jim, you are correct on flue temperature being the main problem for creosote build up. If there is one thing I've learned being a fireman for 20 years and 9 being the Chief is that not keeping flue temps up will cause you a guaranteed chimney fire.

    I can understand those who want to damper down to conserve wood but you are doing ones self an injustice and creating more work or doling out cash for chimney cleaning. On another note some chimneys are just plain built bad and have cold spots, due to many corners or poor insulation qualities.

    I've been burning wood in cook stoves and heat stoves for 30 years and have never had a chimney fire nor have I cleaned the chimney. Seems I always have cleaned others chimneys in the middle of the night.

    Keep your temps up, short periods of smoldering are OK as long as they are followed by a hot burn but over time without the hot burns you will get build up and a chimney fire.

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